Frame grid having the ends of the grid wires connected in a hook formed on the end of each grid bar



Jan. 30, 1968 I 3,366,828

FRAME GRID HAVING THE ENDS OF THE GRID WIRES CONNECTED IN A. SYGALL A HOOK FORMED ON THE END OF EACH GRID BAR Filed April 28, 1965 FIG] 322 11- ,3 FIG 4 INVENTOR. ALFRED SYGALL AGE United States Patent 3,366,828 FRAME GRID HAVING THE ENDS OF THE GRID WIRES CONNECTED IN A HOOK FORMED ON THE END OF EACH GRID BAR Alfred Sygall, London, England, assignor to North American Philips Company, Inc., New York, N.Y., a corporation of Delaware Filed Apr. 28, 1965, Ser. No. 451,454 Claims priority, application Great Britain, Apr. 30, 1964, 18,006/64 4 Claims. (Cl. 313350) ABSTRACT OF THE DISCLOSURE A frame grid having a grid wire wound around a pair of back-bones between two cross-bars, the end of the grid wire being gripped within a hook formed on the end of each cross-bar.

The present invention relates to a frame grid for use in an electron discharge tube comprising a pair of parallel back-bones spaced apart by means of a crossbar secured to the back-bones at each end thereof, a grid wire Eeing wound around the back-bones between the crossars.

It has been proposed to secure the grid wire to the back-bones by adhesion but this is unsatisfactory since the hit commonly used tends to flow between the wound grid wire.

A further method of securing the wire to the backbones is to bend the cross-bars so that the wire is trapped between a cross-bar and a back-bone at its ends. However, it is becoming increasingly popular to employ molybdenum back-bones and molybdenum cross-bars. Unfortunately when molybdenum is welded to molybdenum rather higher temperatures are involved and the molybdenum becomes brittle; when the cross-bar is bent to trap the grid wire it frequently fractures at the welding region.

An object of the present invention is to provide an improved frame grid in which the wire may be mechanically gripped without the crossbar fracturing.

According to the present invention a frame grid for an electron discharge tube comprises a pair of parallel backbones spaced apart by means of a cross-bar at each end of the back-bones and welded to the back-bones, a grid wire wound around the back-bones between the cross-bars, wherein each end of the grid wire is gripped Within a hook formed on the end of the cross-bar. Because the molybdenum is bent at a region spaced from the welding zone, the molybdenum is fairly malleable and so there is less tendency for the cross-bar to fracture.

A second cross-bar may be provided at each end extending parallel to the bent cross-bar so as to provide extra rigidity. Alternatively each cross-bar may be U- shaped in cross-section, one of the limbs being provided with the hook. The back-bone may be profiled to give in creased resistance to bending in a direction parallel to the cross-bars and perpendicular to the back-bones.

Preferably the inner surface of the hook-shaped ends of the cross-bars are coated with a soft metal for example gold, copper or silver; this metal tends to envelop the wire during closing of the hook so as to give better gripping of the grid wire. The material may be heated to approximately 80 C. in air or nitrogen so that it becomes more malleable.

In order that the invention may be readily carried into effect, it will now be described, by way of example, with 3,366,828 Patented Jan. 30, 1968 ice reference to the accompanying diagrammatic drawings, in which:

FIGURE 1 shows a frame grid,

FIGURE 2 shows a cross-section of the frame grid shown in FIGURE 1,

s FIGURE 3 shows a modification,

FIGURE 4 shows a further modification, and

FIGURE 5 shows a detail of yet another modification.

Referring now to FIGURE 1, a frame grid comprises a pair of parallel molybdenum back-bones 1 and 2 spaced apart by means of molybdenum cross-bars 3 and 4. The cross-bars are welded to the back-bones at the places indicated by crosses. A wire grid 5 is wound around the back-bones between the cross-bars, the ends of each crossbar 3 being formed with a hook 6 which is bent as shown to grip the end of the grid wire 5.

FIGURE 2 is a cross-sectional view and serves to illustrate how the wire 5 is gripped by the hook 6. It has been found that a satisfactory grip can be obtained if the end of the hook 6 is formed so that the bend 7 is not too sharp.

FIGURE 3 shows a modification in which, instead of two separate cross-bars 3 and 4, a U-shaped cross-bar 8 is used, a hook 9 being formed at one end. After the wire has been inserted in the hook the hook is closed.

FIGURE 4 illustrates a further modification in which back-bones 10 and 11 are profiled to provide extra strength against bending in a direction perpendicular to the backbones and parallel to the cross-bars.

FIGURE 5 is a detail of a preferred modification in which the inner surface of the hook 6 is coated with a layer 12 of soft material, for example gold, copper or silver. As can be seen from FIGURE 5 when the hook is closed to grip the wire 5 the ductile material tends to flow around the wire and thereby give better gripping action: furthermore it is not necessary to have such a sharp bend as in the case where no coating 12 is used. This tends to decrease the number of fractures occurring at the bend. It is necessary that the material 12 should have a melting point something greater than of the order of 700 C. since during de-gassing and stoving of electron discharge tubes provided with such a frame grid it would otherwise melt.

What is claimed is:

1. A frame grid for use in an electron discharge tube comprising a pair of parallel back-bones spaced apart by means of a crossbar at each end of the back-bones and welded to the back-bones, a grid wire wound around the back-bones between the cross-bars, each end of the grid wire being gripped within a hook formed on the end of the cross-bar, the inner surfaces of the hooks on the cross-bars being provided with a layer of ductile material.

2. A frame grid as claimed in claim 1, wherein the back-bones are profiled to increase their resistance to bending in a direction perpendicular to the back-bones and parallel to the cross bars.

3. A frame grid as claimed in claim 1 wherein the material is gold, copper or silver.

4. A frame grid as claimed in claim 1 wherein the back-bones and the cross-bars are of molybdenum.

References Cited UNITED STATES PATENTS 1,654,899 1/1928 Schwerin 31335O 2,930,923 3/ 1960 Langmack 313-350 3,200,855 8/1965 Wenzel et a1 --71.5

JOHN W. HUCKERT, Primary Examiner. A. J. JAMES, Assistant Examiner. 

